The subject matter disclosed herein relates to controlling fuel flow to a gas turbine engine.
Fuel control of a gas turbine engine revolves around an understanding of the engine combustor and fuel metering characteristics, and ambient conditions, such as temperature and pressure, the engine encounters. Fuel metering can significantly affect the start reliability of a gas turbine engine, such as an auxiliary power unit (“APU”), especially at extreme altitudes and ambient temperatures.
Gas turbine engines may command fuel during starting to achieve a preset acceleration set point curve, whereby a control commands operation between predetermined fuel command maximum and minimum limits. Predetermined fuel command limits take into account a fuel nozzle spray pattern and combustor flame-out limits.
Standard practice is to meter fuel flow based on a speed sensor input signal to maintain a desired acceleration of the engine.